Decathlon exploits left Eaton searching for lost spark

'I feel like a little bit more fragile this year for some reason'

After a stellar 2012 that brought two world records and Olympic decathlon gold, Ashton Eaton was ready for a rest. What he had not bargained for was the physical and mental toll his achievements took out of him.

The American multi-eventer, hailed by sprint king Usain Bolt as the world's greatest athlete, said his exploits have left him this year "feeling physically worn down".

"I feel like a little bit more fragile this year for some reason," Eaton, favourite to win gold at the world championships in Moscow, told a news conference at the Luzhniki stadium on Wednesday.

"I'm usually pretty robust, nothing really bothers me too much. This year, little things have here and there ... and my coach said the year after the Olympics you are kind of physically worn out.

"You see a lot of Olympic champions that are not at this (world championships) meet because it does take a toll on mind and body."

Eaton says he is in great shape in his bid for a first world title

This season he has mixed "a few personal bests earlier this year" with an injury scare when he tweaked his hamstring during high jump practice.

His preparations for Moscow, though, are back on track, and Eaton says he is in great shape in his bid for a first world title after taking silver behind compatriot and two-time winner Trey Hardee in Daegu, South Korea, in 2011.

"I feel ready to go. If something was going to happen (injury-wise), it would have," he said.

The two-day decathlon gets underway on the first morning of the championships on Saturday.